Method and apparatus for feeding and scanning over-sized media sheets

ABSTRACT

A combination automatic document feeder and scanner operates so as to detect automatically an over-sized sheet of media. A linear image sensor detects motion of the oversized document as it is being fed into the scanner in a portrait orientation. A control algorithm responsive to the image sensor functions so those first and second portions of the over-sized sheet are successively registered over the transparent platen of the scanner and scanned. The resulting digital images of the first and second portions of the over-sized sheet are digitally stitched together using a control algorithm that causes 1) a front portion of the oversized document to be advanced a sufficient distance in a forward direction to place the front portion inside the scanning area of the line scanner but not a sufficient distance to place the rear portion of the oversized document inside the scanning area of the line scanner; 2) the line scanner to move in a perpendicular direction to the oversized document to capture indicia information disposed on the front portion of the oversized document; 3) the line scanner to move to a target area below the front portion of the oversized document for capturing a line of indicia information disposed on the front portion of the oversized document; 4) the front portion of the oversized document to advance in a direction perpendicular to the motion of the line scanner in a series of predetermined exposure intervals to determine the distance the oversized document traveled into the scanning area of the line scanner; 5) the line scanner to move in a perpendicular direction to the oversized document to capture indicia information disposed on the rear portion of the oversized document; 6) the front portion indicia information to be combined with the rear portion indicia information without any substantial discontinuity a memory, faxed or printed.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part application of U.S.patent application Ser. No. 09/246,602 filed on Feb. 8, 1999 entitled“Automatic Document Feeder with Improved Sheet Handling Capabilities andMethod of Feeding and Scanning Over-Sized Media Sheets.”

BACKGROUND OF THE INVENTION

[0002] The present invention relates to printers, scanners and faxmachines, and more particularly, to an automatic document feeder that ismore versatile in terms of the size of sheets it can handle.

[0003] Over the past several years, combination printer, scanner and faxmachines have become commercially successful. They can be attached to apersonal computer and function as a traditional printer for printinghigh quality text and/or graphics on a suitable print medium, usuallypaper sheets. The printing may be reliably and economically accomplishedutilizing black and/or color inkjet printer cartridges. Thesecombination machines can also scan documents fed into the same so thattext and/or graphics on the documents can be digitized and inputted intothe personal computer for storage and/or further manipulation. Finally,these combination machines can scan documents fed into the same so thattext and/or graphics on the documents can be sent via modem andtelephone systems to other parties. In some cases these combinationmachines can function as low volume copiers by permitting text and/orgraphics on a document fed into the machine to be scanned and then toimmediately thereafter be printed on a clean sheet from an input papertray. One example of a combination printer, scanner and fax machine withthe foregoing capabilities is the Officejet (Trademark) desktop unitmanufactured and sold by HEWLETT-PACKARD COMPANY, the assignee of thepresent application. See for example U.S. Pat. No. 5,833,381 grantedNov. 10, 1998 and assigned to HEWLETT-PACKARD COMPANY. In this type ofcombination machine individual sheets are fed in a unidirectional mannerfrom an input side of the device, through the device, to an output sideof the device.

[0004] Recently flat bed scanners have become popular peripheral devicesfor use with personal computers. Typically a document is placed flat ona large horizontal glass or transparent plastic platen and a scanninghead reciprocates beneath the transparent platen to generate a veryhigh-resolution digital image of text and/or graphics on the documentfor subsequent computer processing or faxing. In co-pending U.S. patentapplication Ser. No. 09/041,844 filed Mar. 12, 1998 of A. JustineWorley, assigned to HEWLETT-PACKARD COMPANY, and entitled MODULARAUTOMATIC DOCUMENT FEEDER FOR A FLAT BED INPUT DEVICE there is disclosedan automatic document feeder (“ADF”) for sequentially loading andunloading single sheets over a flat bed scanner. A main chassis carriesthe active components of the ADF including paper pick and drivemechanisms for delivering sheets to and from a flat bed scanner, motorsand transmissions for driving the pick and drive mechanisms, a documentbacking assembly and an electronic controller. The main chassis alsoincludes a substantially vertical document input tray. A lower chassisof the ADF includes a low-height form factor, substantially vertical,i.e. inclined, output tray, using paper stiffness caused by apredetermined bending of the outputted sheets to cause the sheets to beself-supporting. Documents are individually fed downwardly and forwardlyfrom the input tray, in a landscape orientation, onto the transparentplaten of the scanner, which scans each document moving in a directiontransverse to the paper feed direction. After the completion of thescanning operation, each document is fed rearwardly and upwardly intothe inclined output tray. An ink jet or laser printer can be providedbeneath the flat bed scanner. The aforementioned ADF does not utilize ascroll-type sheet feed mechanism. It pushes each page instead of relyingon a belt-type advance mechanism.

[0005] The aforementioned ADF is advantageously configured to behingedly mounted to a flat bed scanner to provide a multi-functionproduct that can scan, fax, copy and print. However, problems havearisen with regard to its sheet handling capabilities. Moreparticularly, scanning is designed around an A/A4 scan zone in alandscape orientation only, thus preventing users from scanning andcopying over-sized print media, such as legal and B-size sheets.Furthermore, if over-sized sheets are fed into the output tray inportrait fashion, one or more of the sheets can end up being pushed outof the tray onto the desktop or floor.

SUMMARY OF THE INVENTION

[0006] Accordingly, it would be desirable to provide an ADF with animproved oversized document handling capability.

[0007] According to a preferred embodiment of the present invention, acombination automatic document feeder (ADF) and scanner operates so asto detect automatically an over-sized sheet of media. A linear imagesensor detects motion of the oversized document as it is being fed intothe scanner in a portrait orientation. A control algorithm responsive tothe image sensor functions so that a first and a second portion of theover-sized sheet are successively registered over the transparent platenof the scanner and scanned. The over-sized sheet is thereafter ejectedfrom the scanner into an output tray. The resulting digital images ofthe first and second portions of the over-sized sheet are digitallyrotated and stitched together by a control circuit using the controlalgorithm and the complete image of the over-sized sheet is stored in amemory, faxed or printed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a perspective view of an automatic document feeder (ADF)utilized in accordance with the preferred embodiment of the presentinvention to prevent over-sized media sheets fed in portrait orientationfrom being accidentally driven out of the output tray of the ADF ontothe desktop or floor;

[0009]FIG. 2A is a vertical sectional view of the ADF of FIG. 1 mountedon top of the upper portion of a flat bed document scanner and showing alegal-sized sheet of media resting in the output tray of the ADF inportrait orientation;

[0010]FIG. 2B is a view similar to FIG. 2A showing a legal-sized sheetof media partially ejected into the output tray of the ADF;

[0011]FIG. 2C is a view similar to FIGS. 2A and 2B showing a legal-sizedsheet of media partially ejected into the output tray of the ADF withits leading edge pushing up against a legal-sized sheet of media alreadyresting in the output tray;

[0012]FIG. 3 is a functional block diagram of a combination ADF anddocument scanner utilized in accordance with another aspect of thepresent invention to permit over-sized media sheets to be fed andscanned in portrait orientation;

[0013]FIG. 4 is a flowchart of the operational steps performed by theautomatic document feeder and scanner of FIG. 1 in determining thetravel distances of a moving document to facilitate the reconstructionof scanned image information; and

[0014] FIGS. 5A-D are diagrammatic representations of the ADF and flatbed scanner cooperating in carrying out the operational steps of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Referring to FIG. 1, an automatic document feeder (ADF) 10 isconfigured and adapted to sit on top of a flat bed scanner 12 (FIG. 2A)which is electrically connected to a personal computer (notillustrated). Except as noted hereafter, the construction and operationof the ADF 10 are similar to that disclosed in the aforementionedco-pending U.S. patent application Ser. No. 09/041,844 filed Mar. 12,1998 of A. Justine Worley entitled MODULAR AUTOMATIC DOCUMENT FEEDER FORA FLAT BED INPUT DEVICE, the entire disclosure of which is specificallyincorporated by reference. The ADF 10 (FIG. 1) includes a main chassis14, an upper chassis 16, and a lower chassis 18. When assembled, thethree chassis 14, 16 and 18 form a sheet media path that extendsforwardly from an input tray 22 to an operational station at which islocated a horizontally extending clear glass or transparent plasticplaten 20 (FIG. 2A) of the scanner 12. The media path then extendsrearwardly from the transparent platen 20 to an output tray 24. Theinput tray 22 and the output tray 24 are both curved and aresubstantially vertically oriented, with a slight rearward inclination.The input tray 22 and the output tray 24 are generally parallel with theoutput tray 24 being located behind the input tray 22. The three chassis14, 16 and 18 and the trays 22 and 24 are preferably injection moldedplastic parts.

[0016] The ADF 10 normally receives standard-sized media sheets such aseight and one-half inch by eleven-inch sheets or A4-size sheets, inlandscape orientation, i.e. with the longer dimension running left toright in FIG. 1, perpendicular to the feed direction. A stack of sheetsis loaded into the input tray 22. The input tray 22 is concave in bothvertical and horizontal planes. This double concave shape assists inboth properly aligning the sheets of a multi-sheet document (not shown)and stiffening the document to facilitate sheet feeding without jamming.Sheets are individually picked off the stack in the input tray 22 andfed onto the transparent platen 20 of the flatbed scanner 12. Afterbeing scanning by a transverse motion of an optical scanning head (notillustrated) in the scanner 12, a sheet is then propelled rearwardlyinto the output tray 24. The sheets are normally stored in the outputtray 24 until all of the sheets from the input tray 22 have been scannedand either inputted into the personal computer or sent via facsimile atwhich time they are manually removed from the output tray by anoperator. The output tray 24 also preferably has a double concave shape.This allows a stack of sheets in the output tray 24, which extend aboveand beyond the tray to be self-supporting.

[0017] It will be understood that the scanner 12 is an operationalstation, in the broadest sense, where a function, in this case, opticalscanning, is performed on a media sheet fed to the same. The ADF 10feeds the media sheet to the operational station where a function isperformed on the media sheet. It will be understood that the operationalstation could be a printer or some other device that acts on the mediasheet. The operational function is performed on a stationary sheet inthe case of a scanner and on a moving sheet in the case of a printer.

[0018] The feeding of sheets by the ADF 10 (FIG. 1) is accomplishedsequentially and automatically with the aid of a pick mechanism anddrive rollers described in detail in co-pending application Ser. No.09/041,844 referenced above. A pair of stepper motors such as 26 a and26 b (FIGS. 1 and 3) mounted on either side of the main chassis 14independently drive corresponding rollers via transmissions alsodescribed in said application. The stepper motors are separatelyenergized by a control circuit 27 (FIG. 3) in accordance with firmwareand/or software implemented algorithms to move each sheet of media inthe proper timed sequence from the input tray 22, over the transparentplaten 20 of the scanner 12 and then back into the output tray 24. Theaforementioned combination of the ADF 10 and the flat bed scanner 12 hasthe advantage of allowing multiple scans of an original document whicheliminates the need for the entire document to be scanned into memorywith a single pass of the optical scanning head.

[0019] As best seen in FIG. 1, the ADF 10 is also equipped with an inputtray extender 28 and an output tray extender 30, which are connected to,and project vertically from, the uppermost edges of the input tray 22and output tray 24, respectively. These extenders 28 and 30 facilitatethe handling of over-sized media sheets in portrait orientation, i.e.with their long dimension aligned with the longitudinal direction of themedia feeding.

[0020] When a sheet 32 (FIG. 2B) of media is ejected from a scanningposition on top of the transparent platen 20 its leading portion, whichused to be its trailing portion, has to bend in a curved fashion inorder to conform to the radius of curvature of the output path. Thiscauses its leading edge, which used to be its trailing edge, and itsleading portion to press against those portions of the ADF 10 definingthe output path, if this is the first sheet ejected, or against thepreviously ejected sheet of media. As the leading edge moves higher andhigher up the output path there is more and more surface contact withthe previously ejected sheet. Friction between the sheets builds up,especially if the output tray 24 already contains a stack of ejectedsheets having more than an insubstantial thickness so that the outputpath has been significantly narrowed. In addition, in some officeenvironments, particularly those characterized by very low humidity, asubstantial charge of static electricity will build up between the sheetbeing ejected and the immediately previously ejected sheet of media.This appears to be at least partially a result of the media sheetsrubbing against glass and plastic. When friction, enhanced byelectro-static adhesion between the two overlapping sheets, exceeds theweight of a sheet, then the sheet 34 (FIG. 2C) immediately behind thesheet 32 being ejected will sometimes lift up. Since the output trayextender 30 only extends about three-quarters of the height (length) ofan over-sized sheet of paper fed in portrait orientation, the sheet 34can be pushed completely out of the output tray 24 and onto the desktopor floor. Sheets that are driven completely out of the output tray 24can literally float away and come to rest underneath a piece ofequipment on the desktop, or even onto the floor and underneathfurniture. This type of unintended ejection is very undesirable sincethe operator may not observe this accident and will end up retrieving anincomplete multi-page document from the output tray 24 without knowingthat it is incomplete. Even if the operator does observe the accident,it is tedious to retrieve the sheet that has been improperly ejected andinsert it back into the multi-page document at the correct location andin the correct orientation.

[0021] In order to prevent this type of sheet media “overflow” we havediscovered that the eject motion can be interrupted in a fashion thatunsticks the adjacent sheets, and allows partially lifted sheets in theoutput tray 24 to fall back down to their proper positions. In order toachieve this, the main drive rollers 36 and 38 (FIG. 1) are driven bythe stepper motors 26 a and 26 b so that the media sheet 32 beingejected is only partially ejected from above the transparent platen 20and into the output path, such as seventy percent, for example. The maindrive rollers 36 and 38 are then driven in a reverse direction toretract the media sheet 32 a minute amount, for example one-quarter ofan inch. Thereafter the main drive rollers 36 and 38 are once againreversed to drive the media sheet 32 all of the way into the output tray24. This technique prevents over-sized sheets that are fed through theADF 10 in portrait fashion from spilling out of the output tray 24 overthe top end of the output tray extender 30. Clearly the speed, timingand extent of each media motion-driving segment can be varied whilestill producing the same beneficial result. In general, the “subsequent”media sheet 32 is preferably fed between about one-half andthree-quarters of its way into the output tray 24 before its feedingdirection is momentarily reversed. The subsequent media sheet 32 ispreferably momentarily propelled back out of the tray in rapid fashionso that less than about one-tenth of the subsequent media sheet 32 iswithdrawn from the output tray 24. This ensures that the “previous”media sheet 34, if it has been partially lifted, will fall back down toits rest position using the force of gravity and its inertia. When theprevious media sheet 34 is in its rest position its lowermost edge isengaged with the lower end surface of the output tray 24.

[0022] The ADF 10 can feed standard-sized print media, e.g. standardletter or A4 sheets, in landscape fashion to the scanner 12 which isdesigned around an A/A4 scan zone. The scanning is done by moving theoptical scan head laterally, i.e. transverse to the direction of travelof the sheets. The extenders 28 and 30 permit over-sized media sheetssuch as legal-size and B-size documents to be fed to the scanner 12 inportrait orientation. In such a case the media orientation isperpendicular to the scan zone and scan axis. By adding an additionalsensor to the combination ADF 10 and scanner 12 and providing additionalsoftware/firmware, over-sized media sheets can be scanned in portraitorientation even though the scanner 12 normally only accommodatesstandard-sized media sheets fed in landscape orientation.

[0023]FIG. 3 is a functional block diagram of a combination ADF 10 anddocument scanner 12 that permits over-sized media sheets to be fed andscanned in portrait orientation. A pair of sensors 40 and 42 in the ADF10 normally sense the top and bottom edges of standard-sized media sheetfed by the ADF 10 to the scanner 12 in landscape orientation. Thecontrol circuit 27, which is connected to the sensors 40 and 42, canindependently operate the stepper motors 26 a and 26 b so that ifnecessary the media sheet can be de-skewed by the drive rollers 36 and38. Where an over-sized sheet of media is picked off by the ADF 10 fromthe input tray 22 and fed in portrait orientation a third portraitsensor 44 is interrogated by the control circuit 27. When the controlcircuit 27 determines that there is no sheet outside at least oneportrait margin, the firmware or software feed algorithms utilized bythe control circuit 27 are switched to a portrait mode. The sheet mediais then fed to the drive rollers 36 and 38 where it is de-skewed. Next,a first portion of the sheet media is fed onto the transparent platen 20of the scanner 12 for a predetermined duration to position the sheet toa system reference edge.

[0024] The control circuit 27 next causes the optical scanner head toreciprocate in a left-to-right direction in FIG. 3, transverse to thedirection of travel of the sheet media. The first portion of the sheetmedia is thus scanned and a digital image of its text and/or graphics isgenerated, rotated and stored in a memory part of the control circuit27. The sheet media is then advanced so that a second portion thereof islocated on the transparent platen 20 and scanned, and its digital imagerotated and stored in the memory. In order to permit the scanning of thesecond portion of the media sheet, the first portion must be advancedout of the scan zone. This can be mechanically facilitated by providinga ramp in the forward portion of a scanner housing (not illustrated)similar in configuration to a rear escape ramp. During this process, theleading portion of the over-sized sheet extends through a bezel (notillustrated) in a forward side of the scanner housing. Ribs (notillustrated) can be provided in the main chassis 14 to prevent theadvancing media sheet from snagging on the plastic parts. The output ofone of the sensors 40, 42 or 44 is then used to detect the trailing edgeof the media sheet. The control circuit 27 uses this information inorder to stop the advancement of the media sheet at a predetermined timeso that the second remaining portion will be registered on thetransparent platen 20 to allow the text and/or graphics on the secondportion to be scanned.

[0025] The two stored images are stitched together by the controlcircuit 27 using stored software and/or firmware algorithms. Theresulting complete image is then stored in the personal computer,printed or faxed. The media sheet is then partially ejected rearwardlyfrom the scanner 12 into the output tray 24, momentarily reversed, andthen fully ejected into the output tray 24 to prevent a previouslyejected sheet from being pushed up out of the tray 24 over the extender30.

[0026] Considering now by way of example, a firmware algorithm 400 thatfacilitates the processing of oversized documents traveling from the ADF10 to the scanner 12.

[0027] Before discussing a control algorithm 400 that determines traveldistances of a moving document to facilitate the reconstruction ofscanned image information in an oversized document in a fast andconvenient manner, it may be beneficial to briefly review prior knownsolutions. In this regard, one prior known solution operates by scanningfirst and second halves of a moving document in such a manner to providean overlapping region. The overlapping regions of the two image halvesare then processed to determine the relative image translation. Whilethis method may provide an oversized image, the method has two majordisadvantages. First, the method is computationally intensive forimplementation on an embedded processor. Secondly, such a methodgenerally suffers from aliasing problem with images that have regularpatterns.

[0028] Considering now the control algorithm 400 in greater detail withreference to FIGS. 4 and 5A-D, the control algorithm 400 processes imagedata by first correlating each row (n) of a scanned image to a rowcaptured later in time (This row is offset in the image by the step sizeso as to provide row (n+step)). A correlation of the two rows (row n androw n+step) is achieved by accumulating the absolute difference betweenthe pixels over a range of row offsets to find the best fit defined byminimum error (This step avoids the multiplication required to implementa standard correlation fuinction). Finally, the row offsets from thecorrelation are accumulated and divided by the step size to determinethe total distance the document moved.

[0029] It should be noted that the range of the offsets that must bechecked for the best correlation is limited by assuming the documentwill not move backwards and that the document has a maximumacceleration. The order in which the offsets are checked is alsooptimized to increase the probability that the best-correlated offsetwill be tested early. This allows the subsequent tests to be abortedsooner when their error accumulates above the best fit.

[0030] Considering now the algorithm 400 in still greater detail withreference to FIGS. 4 and 5A-D, the control algorithm begins at a startcommand 402 when the ADF 10 causes an oversized document D to betransported onto the document receiving area of the scanner 12, as bestseen in FIG. 5A. (In this regard, the oversized document is transportedso that its leading edge or its front half portion is transported intothe document pick up or scanning area 20 of the scanner 12 while itstrailing edge or rear half portion is positioned outside the documentscanning area 20 of the scanner 12.) With the oversized document sopositioned by the ADF 10, the control algorithm 400 advances to acommand step 403 that causes the optical scanner head or line scanner 13(FIG. 3) to move below and pass below the front half portion of thedocument so that the indicia information on that portion of the documentis scanned. This information is utilized by the algorithm 400 todetermine an optimal location for collecting the positioning informationas will be explained hereinafter in greater detail. Next, the algorithm400 advances to a command step 404 that causes the line scanner 13 to bere-positioned to a stationary location below the target document richwith indicia information as best seen in FIG. 5B.

[0031] With the line scanner 13 held in a stationary position, thecontrol algorithm advances to a command step 406 and a command step 408to start saving lines of data captured by the scanner 12. That is thecontrol algorithm 400 causes the line scanner 13 to capture data, row byrow, as the ADF 10 moves the document in a forward directionperpendicular to the line scanner 13. That is, data is collected fromthe line scanner 13 at fixed intervals (exposure times) and placed in abuffer 15 that is sufficiently large in capacity to store a multiplenumber of rows.

[0032] From the foregoing, those skilled in the art should understandthat data is collected by causing the line scanner 13 to be placed in anoptimal position to capture the indicia information on the front half ofthe document as the document is advancing in a forward direction off ofthe image capture area 20 of the scanner 12. The buffer 15 issufficiently large to store the indicia information for all rows scannedduring the time the document is being advanced in a directionperpendicular to the line scanner 13. By way of example, with a 3.8millisecond exposure time, a buffer of about 400 lines is sufficient.

[0033] The action of advancing the document from the ADF 10 also causesthe rear half portion of the document to be moved into the image capturearea 20 of the scanner 12 for the subsequent capture of the indiciainformation disposed on the rear half of the document. (FIG. 5C)

[0034] Once the paper move has been completed (by the ADF), the controlalgorithm 400 terminates the saving information actions by advancing toa command step 410. The data buffer now contains a series of rows suchthat adjacent rows only differ by the amount of target or documentmotion during a single exposure interval. In order to improve theaccuracy of correlation between rows of captured data, the algorithmproceeds to a command step 412 that pre-processes the buffer datautilizing a unidimensional gradient filter that extends along the axisof the line scanner 13.

[0035] In order to determine the step size or motion distance betweenrows, the program advances to a command step 414 that causes thecorrelation of a buffer row (n) with another row captured at a latertime. The program then advances to a command step 416 that accumulatesthe translation determined by the correlation. It should be understoodby those skilled in the art that when multiple correlations areperformed for each row they can be averaged together or the strength ofthe correlation can be utilized to favor the best signals.

[0036] Next, the program goes to a decision step 418 to determinewhether the last buffered row captured was the last row. If the currentbuffered row captured is not the last buffer row of the front halfportion of the document, the program returns to sep 414 and proceeds asdescribed previously.

[0037] If a determination is made a step 418, that the current bufferrow is the last buffer row, the program advances to a command step 420that utilizes the accumulated translation between rows to calculate atotal translation figure.

[0038] Once the translation vector from the first or front half of thedocument has been determined, the program goes to a command step 422that causes the second or rear half portion of the document to bescanned in the same manner as previously described relative to the fronthalf of the document. (FIG. 5D)

[0039] The program then proceeds to a command 424 that combines thefirst and second halves of the document using the translation vector toeffect stitching without any substantial discontinuity being formedbetween the two halves. The program then advances to an end command 426.

[0040] While in the preferred embodiment of the present invention, thecontrol algorithm 400 has been described as first moving the front halfof the document into the scanning area 13 of the scanner, those skilledin the art will appreciate that a reverse process could just as well beemployed where the front half of the oversized document is drivenoutside the scanning area 13 allowing the rear half of the document tobe scanned first. The row data would then be gathered by using the ADF10 to retract the rear half of the document in a series of predeterminedinterval steps. The translation vector would be determined in the samemanner with scanning of the first or front half of the document beingaccomplished prior to combining the two halves.

[0041] Whereas we have described preferred embodiments of ourcombination ADF and scanner and improved methods of operating the sameto prevent overspill and allow the scanning of over-sized media sheet inportrait orientation, it will be apparent to those of ordinary skill inthe art that our invention may be modified in both arrangement anddetail. For example, when ejecting a sheet of media into the outputtray, it may be difficult and/or complex to momentarily reverse thedirection of travel of the sheet. Beneficial results can also beachieved if the ejection motion is momentarily stopped to allow aprevious sheet that is being lifted to fall back down into the outputtray under the force of gravity. It will of course be understood thatwhere the media sheet is partially ejected into the output tray and thenits direction of travel is reversed, it will momentarily stop beforemoving in the reverse direction. Momentary reversal during ejection isthus a species of the invention that involves momentary stopping duringejection. Therefore, the protection afforded our invention should onlybe limited in accordance with the scope of the following claims.

We claim:
 1. A method of scanning an oversized document having a frontportion and a rear portion, the oversized document having an areadimension in excess of a document scanning area of a line scanner,comprising: advancing the front portion of the oversized document asufficient distance in a forward direction to place the front portion ofthe oversized document inside the scanning area of the line scanner butnot a sufficient distance to place the rear portion of the oversizeddocument inside the scanning area of the line scanner; moving the linescanner in a perpendicular direction to the oversized document tocapture indicia information disposed on the front portion of theoversized document; positioning the line scanner in a target area belowthe front portion of the oversized document for capturing a line ofindicia information disposed on the front portion of the oversizeddocument; advancing the front portion of the oversized document in adirection perpendicular to the motion of the line scanner in a series ofpredetermined exposure intervals to determine the distance the oversizeddocument traveled into the scanning area of the line scanner; moving theline scanner in a perpendicular direction to the oversized document tocapture indicia information disposed on the rear portion of theoversized document; and combining the front portion indicia informationwith the rear portion indicia information without any substantialdiscontinuity between the two portions.
 2. A method of determiningdocument travel distance, comprising: advancing a front portion of anoversized document a sufficient distance along a lateral scan path of aline scanner to provide a first portion of a single line of indiciainformation; and calculating a translation vector indicative of adistance between a last row in said first portion of the single line ofindicia information and a first row in a second portion of the singleline of indicia information disposed on a rear portion of said oversizeddocument.
 3. A method of stitching together scanned indicia imageinformation from a front portion and a rear portion of an oversizeddocument, comprising: advancing a scanned front portion of the oversizeddocument a sufficient distance along a scanning line of a line scannerto capture a last row in a front portion of a line of scanned imageinformation disposed on the front portion of the oversized document; andadvancing said line scanner in a scan path perpendicular to a directiontraveled by the oversized document to capture a rear portion of the linedisposed on the rear portion of the oversized document; and combiningsaid last row in the front portion of the line of scanned imageinformation disposed on the front portion of the oversized document withsaid line of scanned information disposed on the rear portion withoutcausing any substantial discontinuity between said front portion of theline and said rear portion of the line.
 4. A method of scanningover-sized sheets of media having N rows of image information,comprising: moving an over-sized sheet and scanner relative to oneanother to facilitate the scanning of image information disposed on saidover-sized sheet; scanning a row of image information for generating aset of pixels indicative of said row of image information; scanninganother row of image information for generating another set of pixelsindicative of said another row of image information, said another row ofimage information being offset from said row of image information by apredetermined step size; accumulating an absolute difference betweenpixels over a range of offsets to find a minimum error correlationvalue; repeating said steps of moving, scanning, scanning andaccumulating a sufficient number of times to accumulate a set of rowoffset values; dividing said set of row of offset values by saidpredetermined step size to determine the total distance the over-sizedsheet and scanner have moved relative to one another; and repeating allof the preceding steps a sufficient number of times until the entireoversized sheet has been scanned.
 5. A method of automatically scanningover-sized sheets of media fed from an automatic document feeder inportrait orientation utilizing a scanner adapted to scan standard-sizeddocuments in landscape fashion by moving an optical scanning head in adirection transverse to a direction of travel of sheet media fed intothe scanner by the automatic document feeder, comprising: picking anover-sized sheet of media from an input tray and propelling the sheet ina forward direction; advancing a first portion of the over-sized sheetinto the scanner; scanning the first portion of the over-sized sheet ina single pass of the optical scanning head; generating a first digitalimage of the text and/or graphics on the first portion of the oversizedmedia sheet; storing the first digital image in the memory; advancing asecond remaining portion of the over-sized sheet into the scanner;scanning the second portion of the over-sized sheet in a single pass ofthe optical scanning head; generating a second digital image of the textand/or graphics on the second portion of the oversized media sheet;storing the second digital image in the memory; rotating and stitchingthe first and second digital images together to generate a third digitalimage representing the entire text and/or graphics on the over-sizedmedia sheet; storing the third image in the memory; and propelling thescanned oversized sheet of media out of the scanner and into an outputtray of the automatic document feeder.
 6. The method of claim 5, whereinthe output of a sensor in a media path is used to detect the trailingedge of the oversized media sheet in order to register the firstremaining portion of the media sheet on a transparent platen of thescanner in the appropriate position to allow the text and/or graphics onthe first portion to be scanned.
 7. A method of gathering indiciainformation from an oversized document, comprising: correlating each row(n) of a scanned image to a row captured later in time so as to providean offset step function; accumulating an absolute difference between arange of offsets values; and dividing the accumulated offset values toprovide a total distance vector value to combine a rear half portion ofthe oversized document with a front half portion of the oversizeddocument without any substantial discontinuity between the two halves ofthe document.
 8. A method of gathering indicia information from anoversized document having a front half portion and a rear half portion,where the two portions in combination exceed the scanning area of ascanner, comprising: advancing the oversized document in a forwarddirection a sufficient distance into a scanning area to position thefront half portion outside the scanning area of the scanner and the rearhalf portion in the scanning area of the scanner; moving the oversizeddocument in a reverse direction in a series of predetermined intervalsto capture each row of indicia information on the rear half portion ofthe document without capturing any indicia information on the front halfportion of the document; moving the oversized document in a furtherreverse direction in another series of predetermined intervals tocapture each row of indicia information on the front half portion of thedocument without capturing any indicia information on the rear halfportion of the document; and combining the indicia information from therear half of the oversized document with the indicia information fromthe front half of the oversized document without any substantialdiscontinuity between the two halves of the document.
 9. A documentscanning system, comprising: an input device having a line scanner and adocument receiving area; an automatic document feeder mounted to saidinput device for moving an oversized document into said documentreceiving area, said document receiving area being for receiving thewhole of said oversized document; and a control program for causing saidautomatic document feeder to move a front portion of said oversizeddocument into said document receiving area and for causing said linescanner to travel along a rectilinear path of travel adjacent saiddocument receiving area to facilitate the capturing of informationdisposed on the whole of the front portion of said oversized document;said control program for further causing said automatic document feederto incrementally advance the front portion of said oversized documentout of said document receiving area along a path perpendicular to thepath traveled by said line scanner and for causing said line scanner tobe held in a stationary position during the advancing of the frontportion to facilitate calculating a total translation vector between thefront portion of said oversized document and a rear portion of saidoversized document; said control program still further causing said linescanner to again travel along said rectilinear path of travel tofacilitate the capturing of information disposed on the whole of therear portion of said oversized document and for using said translationvector to stitch together the captured information from the frontportion and the rear portion of the oversized document withoutintroducing any substantial discontinuity between the front portion andthe rear portion.
 10. In combination with an automatic document feederand line scanner, a document control device, comprising: a line scannercontrol for moving the line scanner in a rectilinear path of travel tocapture in a first past indicia information disposed on a front portionof an oversized document and to capture in a second past indiciainformation disposed on a rear portion of said oversized document; saidline scanner control further for moving said line scanner to adetermined stationary position beneath said front portion to facilitatethe capturing of position information to calculate an incrementaldistance traveled by said front portion during a predetermined timeperiod; and an automatic document feeder control for moving said frontportion and said rear portion in unison between said first past and saidsecond pass to position said rear portion in a location that facilitatesthe capturing of indicia information disposed thereon.